The role of impulse oscillometry in the management of asthma when forced expiratory maneuvers are contraindicated: case series and literature review.

Objectives: The impulse oscillometry system (IOS) provides an alternative method of lung function testing for patients in whom forced expiratory manoeuvres are contraindicated, such as those with inherited vascular connective tissue disorders. Here we examine the role of IOS in the diagnosis and monitoring of asthma in such patients through a clinical case series and literature review.Methods: The clinical case series comprised of data from 12 patients with inherited connective tissue disorders representing 32 clinical encounters. Of these, 11 encounters were for asthma diagnosis and 21 were for asthma monitoring. Symptoms, exhaled nitric oxide (FeNO) and IOS were assessed at each encounter.Results: In the clinical case series, 5 of 6 patients with likely asthma (as determined by physician review and exhaled nitric oxide testing) had abnormal IOS parameters compared with 0 of 5 of those with unlikely asthma. In the monitoring group, 11 encounters resulted in treatment escalation (demonstrating suboptimal control), and 8 resulted in no change to treatment (good control). Six of 11 of those with suboptimal control had abnormalities in ≥3 IOS parameters, with R5 and R5-20 most frequently affected. Only 1 of 8 of those with good control had abnormalities in ≥3 IOS parameters.Conclusions: IOS can be used as an alternative to conventional lung function testing to support the diagnosis and monitoring of asthma when forced expiratory manoeuvres are contraindicated. Larger studies are required to establish severity and treatment escalation thresholds and provide clearer comparisons with spirometry values.

Pericoronary and periaortic adipose tissue density are associated with inflammatory disease activity in Takayasu arteritis and atherosclerosis.

AIMS: To examine pericoronary adipose tissue (PCAT) and periaortic adipose tissue (PAAT) density on coronary computed tomography angiography for assessing arterial inflammation in Takayasu arteritis (TAK) and atherosclerosis. METHODS AND RESULTS: PCAT and PAAT density was measured in coronary (n = 1016) and aortic (n = 108) segments from 108 subjects [TAK + coronary artery disease (CAD), n = 36; TAK, n = 18; atherosclerotic CAD, n = 32; matched controls, n = 22]. Median PCAT and PAAT densities varied between groups (mPCAT: P < 0.0001; PAAT: P = 0.0002). PCAT density was 7.01 ± standard error of the mean (SEM) 1.78 Hounsfield Unit (HU) higher in coronary segments from TAK + CAD patients than stable CAD patients (P = 0.0002), and 8.20 ± SEM 2.04 HU higher in TAK patients without CAD than controls (P = 0.0001). mPCAT density was correlated with Indian Takayasu Clinical Activity Score (r = 0.43, P = 0.001) and C-reactive protein (r = 0.41, P < 0.0001) and was higher in active vs. inactive TAK (P = 0.002). mPCAT density above -74 HU had 100% sensitivity and 95% specificity for differentiating active TAK from controls [area under the curve = 0.99 (95% confidence interval 0.97-1)]. The association of PCAT density and coronary arterial inflammation measured by 68Ga-DOTATATE positron emission tomography (PET) equated to an increase of 2.44 ± SEM 0.77 HU in PCAT density for each unit increase in 68Ga-DOTATATE maximum tissue-to-blood ratio (P = 0.002). These findings remained in multivariable sensitivity analyses adjusted for potential confounders. CONCLUSIONS: PCAT and PAAT density are higher in TAK than atherosclerotic CAD or controls and are associated with clinical, biochemical, and PET markers of inflammation. Owing to excellent diagnostic accuracy, PCAT density could be useful as a clinical adjunct for assessing disease activity in TAK.

Study of indications for cardiac device implantation and utilisation in Fabry cardiomyopathy.

BACKGROUND: Fabry disease is a treatable X-linked condition leading to progressive cardiomyopathy, arrhythmia and premature death. Atrial and ventricular arrhythmias contribute significantly to adverse prognosis; however, guidance to determine which patients require cardiovascular implantable electronic devices (CIEDs) is sparse. We aimed to evaluate indications for implantation practice in the UK and quantify device utilisation. METHODS: In this retrospective study, we included demographic, clinical and imaging data from patients in four of the largest UK Fabry centres. Ninety patients with Fabry disease were identified with CIEDs implanted between June 2001 and February 2018 (FD-CIED group). To investigate differences in clinical and imaging markers between those with and without devices, these patients were compared with 276 patients without a CIED (FD-control). RESULTS: In the FD-CIED group, 92% of patients with permanent pacemakers but only 28% with implantable cardioverter-defibrillators had a class 1 indication for implantation. A further 44% of patients had defibrillators inserted for primary prevention outside of current guidance. The burden of arrhythmia requiring treatment in the FD-CIED group was high (asymptomatic atrial fibrillation:29%; non-sustained ventricular tachycardia requiring medical therapy alone: 26%; sustained ventricular tachycardia needing anti-tachycardia pacing/defibrillation: 28%). Those with devices were older, had greater LV mass, more scar tissue and larger atrial size. CONCLUSIONS: Arrhythmias are common in Fabry patients. Those with cardiac devices had high rates of atrial fibrillation requiring anticoagulation and ventricular arrhythmia needing device treatment. These are as high as those in hypertrophic cardiomyopathy, supporting the need for Fabry-specific indications for device implantation.

Familial pneumothorax: towards precision medicine.

One in 10 patients suffering from primary spontaneous pneumothoraces has a family history of the disorder. Such familial pneumothoraces can occur in isolation, but can also be the presentation of serious genetic disorders with life-threatening vascular or cancerous complications. As the pneumothorax frequently precedes the more dangerous complications by many years, it provides an opportunity to intervene in a focused manner, permitting the practice of precision medicine. In this review, we will discuss the clinical manifestations and underlying biology of the genetic causes of familial pneumothorax.

An unusual finding in a 57-year-old woman with new onset hypertension and a diastolic murmur.

CLINICAL INTRODUCTION: A 57-year-old woman presented to our clinic with breathlessness brought on while walking uphill. She had been recently diagnosed with systemic hypertension. There was no known family history of cardiac disease, or prior smoking habit. On examination, pulse was 73 bpm and blood pressure 155/73 mm Hg, which was asymmetrical in her arms. Auscultation revealed a readily audible early diastolic murmur in the aortic area and bilateral subclavian bruits. ECG showed sinus rhythm with no abnormality. Transthoracic echocardiography demonstrated mild-to-moderate aortic regurgitation, and normal left ventricular size and function. The ascending aorta was mildly dilated (41 mm), with para-aortic thickening noted. Owing to the abnormal appearance of the aortic wall, cardiac MRI, and subsequently 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET) scan was performed (figure 1). QUESTION: Which complication of the underlying disease is evident in figure 1, panel C? Aortic aneurysmAortic dissectionAortic thrombusCoronary artery aneurysmCoronary sinus fistula.

Dynamics of the tricuspid valve annulus in normal and dilated right hearts: a three-dimensional transoesophageal echocardiography study.

BACKGROUND: The tricuspid valve annulus (TVA) is a complex three-dimensional structure that is incompletely understood. Three-dimensional transoesophageal echo (TOE) provides us with the opportunity to examine this structure in detail. METHODS AND RESULTS: Fifty patients were included, divided into two groups: controls (n = 20), and dilated right hearts (DRH, n = 30). Three-dimensional zoom images of the TVA were acquired using an iE33 machine and X7-2t transducer. Antero-posterior (AP) diameter, septo-lateral (SL) diameter, area, circumference, and height were measured at 6 points of the cardiac cycle adapting commercially available software designed for assessing the mitral valve (MVQ, Philips). The eccentricity ratio was calculated as AP/SL. The tricuspid annular area decreases during systole in both groups, and is greatest in mid-diastole. The area is significantly larger in the DRH group (mean 1566 mm(2) DRH vs. 1097 mm(2) controls; P < 0.01). The SL diameter increases proportionately more in the DRH group, resulting in a more circular orifice and lower eccentricity ratios (eccentricity ratio mean 1.01 DRH vs. 1.24 controls; P < 0.01). The dynamic diastolic to systolic change in the SL diameter is lost in patients with DRH, contributing to the more circular TVA orifice throughout systole. CONCLUSION: Three-dimensional TOE allows us to examine the TVA in great detail. In patients with DRH, the TVA dilates in a SL direction, resulting in a more circular orifice. The dynamic changes of the TVA are lost in patients with DRH, potentially contributing to functional tricuspid regurgitation.

Transthoracic real-time three-dimensional echocardiography offers additional value in the assessment of mitral valve morphology and area following mitral valve repair.

AIMS: The accurate postoperative assessment of mitral valve repair is important not only to document operative outcome, but also to confirm the functional morphology of the repaired valve. METHODS AND RESULTS: We assessed 25 consecutive patients following mitral valve repair with transthoracic real-time 3-dimensional echocardiography (RT3DE) and 2-dimensional echocardiography (2DE). We compared the adequacy of the visualization of the mitral valve Carpentier segments, the site of the repair, and the accuracy of planimetry by RT3DE and 2DE in estimating the postoperative mitral valve area (MVA), compared to the Doppler-derived pressure half-time (PHT) value. Inter-observer variability and feasibility were also assessed for RT3DE. Adequate visualization of the mitral valve segments was more frequently obtained by 3DE imaging (163/170 by 3DE vs. 121/170 by 2DE, P < 0.001). In particular, the mitral valve commissures were more clearly identified with 3DE. 3DE also was significantly better at correctly identifying the site of the repaired segment (26/30 by 3DE vs. 19/30 by 2DE, P < 0.05). The difference in MVA (mean difference +/- SD) determined by 3DE planimetry, when compared to PHT was -0.21 +/- 0.46 cm(2) and -0.44 +/- 0.95 cm(2) for 2DE (P = 0.014). Planimetry by 3DE more closely correlated with the MVA calculated by PHT than 2DE planimetry (r = 0.89 for 3DE vs. r = 0.6 for 2DE). Imaging with RT3DE was both feasible, with a mean acquisition time of 4.02 +/- 1.68 min, and data analysis time of 15.82 +/- 3.9 min, and reproducible, with good inter-observer variability for segment scoring with 3DE (kappa = 0.79) and mean inter-observer difference in assessing MVA by 3DE planimetry of 0.18 +/- 0.12 cm(2) (P = NS). CONCLUSION: This study suggests that RT3DE offers additional morphological postoperative data of repaired mitral valves, and increases the accuracy of MVA estimation by planimetry. It is both feasible in a busy echocardiography department and reproducible.

Measurement of cardiac output by real-time 3D echocardiography in patients undergoing assessment for cardiac transplantation.

AIMS: Heart transplant assessment includes cardiac output calculation by right heart catheterisation. Real-time 3D echocardiography (RT-3DE), unlike 2D echocardiography, can measure stroke volume without inaccurate geometrical assumptions. The purpose of this study was to assess the feasibility and accuracy of non-invasive RT-3DE cardiac output calculation. METHODS AND RESULTS: Forty consecutive patients referred for transplant assessment underwent transthoracic RT-3DE. Full volume 3DE data sets were acquired from apical views with the iE33 ultrasound system (Philips Ultrasound, Bothell, USA). Four patients were excluded due to poor image quality. The remaining 36 patients had end-diastolic (LVEDV) and end-systolic (LVESV) left ventricular volumes manually traced, using endocardial detection software. Cardiac output was subsequently calculated: [(LVEDV - LVESV) x heart rate]. Thermodilution derived cardiac outputs, under the same haemodynamic conditions, were used as reference for comparison. There was close correlation between RT-3DE and catheter derived cardiac outputs (r = 0.91, y = 0.86x + 0.45, SEE 0.39 L/min, mean difference from reference -0.06 L/min, SD 0.40 L/min). RT-3DE data analysis took 3 min per case. CONCLUSION: This study shows RT-3DE is an accurate method for calculating cardiac output. In patients requiring serial evaluation of cardiac function, this non-invasive test may be preferable to invasive right heart catheterisation.

Real-time 3-dimensional echocardiography for quantification of the difference in left ventricular versus right ventricular stroke volume in a chronic animal model study: Improved results using C-scans for quantifying aortic regurgitation.

OBJECTIVE: The purpose of our study was to test the applicability of calculating the difference between left ventricular (LV) and right ventricular (RV) stroke volume (SV) for assessing the severity of aortic (Ao) regurgitation (AR) using a real-time 3-dimensional (3D) echocardiographic (RT3DE) imaging system. METHODS: The Ao valve was incised in 5 juvenile sheep, 6 to 10 weeks before the study, to produce AR (mean regurgitant fraction = 0.50). Simultaneous hemodynamic and RT3DE images were obtained on open-chest animals with Ao and pulmonary flows derived by Ao and pulmonary electromagnetic flowmeters balanced against each other. Four stages (baseline, volume loading, sodium nitroprusside, and angiotensin infusion) were used to produce a total of 16 different hemodynamic states. Epicardial scanning was done with a 2.5-MHz probe to sequentially record first the RV and then the LV cavities. Cavity volumes from the 3D echocardiography data were determined from angled sector planes (B-scans) and parallel cutting planes (C-scans, which are planes perpendicular to the direction of the volume interrogation). AR volumes were determined from 3D images by computing and then subtracting RV SVs from LV SVs and then these were compared with electromagnetic flowmeter-derived SV and regurgitant volumes. RESULTS: There was close correlation between RV and LV SVs of the RT3DE and electromagnetic methods (C-scans: LV, r = 0.98, standard error of the estimate [SEE] = 2.62 mL, P =.0001; RV, r = 0.89, SEE = 2.67 mL, P <.0001; and B-scans: LV, r = 0.95, SEE = 3.55 mL, P =.0001; RV, r = 0.77, SEE = 2.78 mL, P =.0003). Because of the small size of the RV in this model, the correlation was closer for C-scans than B-scans for RV SV. AR volume estimation also showed that C-scan (r = 0.93, SEE = 4.23 mL, P <.0001) had closer correlation than B-scan (r = 0.89, SEE = 4.87 mL, P <.0001). However, B-scan-derived AR fraction showed closer correlation than did C-scan (r = 0.82 vs r = 0.85, respectively). CONCLUSION: In this animal model, RT3DE imaging had the ability to reliably quantify both LV (B- and C-scans) and RV SVs and to assess the severity of AR.

Strain rate acceleration yields a better index for evaluating left ventricular contractile function as compared with tissue velocity acceleration during isovolumic contraction time: an in vivo study.

OBJECTIVE: Our study aimed to investigate whether strain rate acceleration (SRA) during isovolumic contraction time (IVCT) could serve as a sensitive indicator of myocardial function. METHODS: A total of 8 sheep underwent occlusion of left anterior descending coronary artery or diagonal branches and 2 sheep underwent left circumflex coronary artery occlusion to create septal, apical, or basal segment myocardial ischemia 19 to 27 weeks before the study. Baseline, volume-loading, dobutamine, and metoprolol infusion were used to produce 4 hemodynamic stages for each sheep. Doppler tissue imaging was acquired using a 5-MHz probe (GE/VingMed Vivid Five, GE Medical Systems, Milwaukee, Wis) on open-chest animals using the liver as a standoff at the apex. Using software (EchoPac, GE Medical Systems), SRA during IVCT was calculated and compared with tissue velocity acceleration (TVA) during IVCT from areas located in the normal and ischemic zones. Also, invasively monitored left ventricle dP/dt was measured as reference contractile function. RESULTS: Both TVA and SRA during IVCT showed higher values for normal tissue than for ischemic area (P <.0001). SRA for normal wall segments changed significantly during the 4 stages (P =.01) with corresponding changes on high-fidelity left ventricular pressure catheters (r = 0.92). TVA over normal segments showed no significant change (P =.29) in the 4 hemodynamic stages. Both TVA and SRA of the ischemic segments showed no significant change with pharmacologic maneuvers or loading conditions. CONCLUSIONS: SRA and TVA during IVCT are both useful indicators for detecting abnormal heart wall motion. However, SRA tends to be more sensitive than TVA for differentiating the response to stress conditions.

Will a handheld ultrasound scanner be applicable for screening for heart abnormalities in newborns and children?

BACKGROUND: There is significant interest in opportunities to provide echocardiography services for detection of congenital heart disease with portable, or even handheld, devices in remote areas or third world countries where conventional ultrasound systems may not be available. We tested a handheld system (HHS) (SonoHeart, SonoSite Inc, Bothell, Wash) equipped with a broadband, 7- to 4-MHz, miniaturized, curved, linear-array transducer and implemented with an improved directional Doppler flow map. METHODS: All echocardiography scanning was performed in the neonatal nursery, pediatric intensive care department, or pediatric echocardiography laboratory of our institution. We reviewed limited echocardiography view sequences sequentially obtained by the same expert examiner (D.J.S.) in 50 infants and children (age: 1 day to 6 years), with preoperative or postoperative forms of congenital heart disease. Each patient was studied twice, once with a conventional full-feature system (FFS) and then a limited scan with the HHS using similar frequency transducers. The cardiologist (D.J.S.) and blinded research laboratory reviewers (X.L., G.K.M., R.A.R.) read the FFS and HHS image sequences for diagnosis and for grading the quality of the anatomic and flow feature images. The studies were performed and reviewed with the examiner and reviewers blinded to patient diagnosis. RESULTS: The major diagnoses (eg, patent ductus arteriosus, atrio-ventricular (AV) canal, peripheral pulmonary valve stenosis, aortic coarctation, atrial septal defect, ventricular septal defect, preoperative or postoperative tetralogy of Fallot, and mitral regurgitation) were made by both readers, who were unaware of each other's diagnosis results. Furthermore, the average composite HHS cardiac anatomic feature score on a scale of 0 (not visualized) to 3 (visualized precisely) from the parasternal long-axis and 4- or 5-chamber view for cardiac anatomy were 2.67 +/- 0.49 (SD) and 2.50 +/- 0.55, respectively, versus 2.73 +/- 0.45 and 2.55 +/- 0.54 for the FFS. The mean flow feature score, comprising all views, was 2.67 +/- 0.45 (HHS) versus 2.72 +/- 0.48 (FFS). The P values for all above comparisons were >.05. Image quality of the FFS anatomic structures were, thus, not statistically different from the HHS. Although the color cosmetic was different for the HHS directional (nonvelocity) map, only 9% of 150 total findings (including structural abnormalities and flow features, none of which were critical) were missed, whereas the other 91% regurgitant, shunt, stenosis flow features or heart structure were imaged adequately by the HHS in this population. CONCLUSIONS: Implementing high-frequency transducers and programs optimized for tissue and flow imaging on the HHS should provide images of sufficient quality for targeted echocardiography examinations to determine the presence, absence, or status of congenital heart disease in newborns and young children.

Lower receiving frequencies than transmitting frequencies could yield improved results for contrast imaging: an in vivo study in closed chest canines.

BACKGROUND: Ultrasonic imaging methods of receiving at higher frequencies, which are multiples of the transmitting frequencies (harmonic imaging), are well established as a means of improving myocardial visualization in association with intravenous contrast administration. This exploratory study examined the effect of using receive frequencies that were lower than the transmit frequencies while imaging closed chest dogs with an Ensemble wideband, phase inversion contrast program on a modified Siemens Elegra scanner. METHODS: Intravenous bolus injections of 0.75 mL Definity and 1 mL QW7437 were administered to six anesthetized dogs. Intermittent imaging for contrast visualization was performed using either a broadband array, transmitting at 1.4 MHz and receiving at 2.6-3.2 MHz or a broadband 4-7.5 MHz transducer transmitting at 6.0 MHz and receiving at 4.2-4.5 MHz. Contrast enhancement was measured by videodensitometry, sampling mid-cavity and within the myocardium before and after injection. The changes in videodensity from control to after injection were calculated for each method. RESULTS: There was no significant difference in the change in intracavity videodensity between the two imaging strategies although there was near full intracavity saturation in all cases. However, the change in myocardial density was significantly greater for both contrast agents when using receiving frequencies lower than transmitting frequencies (P = 0.02 and 0.03). The difference in duration of the myocardial blush did not reach statistical significance but it tended to persist for longer with the lower receiving frequencies. CONCLUSION: Delivering sound energy at a slightly higher frequency and receiving at lower than the transmit frequency may be an advantageous method of enhancing myocardial perfusion signals during intravenous contrast echocardiography.

Strain rate imaging: an in vitro "validation" study using a physiologic balloon model mimicking the left ventricle.

BACKGROUND: Strain rate imaging (SRI) can be implemented from digital ultrasound loops of tissue Doppler imaging (TDI) data and is performed as an autocorrelation solution of the distance between intramyocardial targets. As such, it should have better resolution along longer distances of wall segments that are imaged at the length of individual ultrasound scan lines. METHODS: We used a new left ventricular double-balloon phantom with a tissue-mimicking gel between the walls. Mounted in a water bath and connected to a pulsatile flow pump at four-stroke volume (30-50 ml/beat), the high frame rate, digital, multiple two-dimensional/tissue/TDI loops of balloon wall motion were recorded using a GE VingMed system FiVe (3.5 MHz phased array transducer), with the model scanned longitudinally from the apex. The strain rate (SR) values were measured at the apex and the lateral wall using an offline measurement program, and mean SR values for every 100 msec were calculated by averaging three determinations at each point. The excursions of the apex and lateral wall also were measured directly by high speed digital video imaging, and consecutive velocity profiles were calculated every 100 msec. A total of 40 data points for four-stroke volumes were analyzed. RESULTS: While our balloon model had enough gel targets between the walls to produce a good mimic of myocardial speckle with walls that thickened and thinned, samples immediately across the apex and apex SR values (Hz) varied substantially. In contrast, systematic signals could be obtained from lines imaged >15 degrees from the true apex and crossing a longer length of myocardium. At the lateral wall, there was a close correlation between the video velocities and SR values, as well as a close overlap of the phasic patterns. CONCLUSIONS: SRI produces more reliable data from wall segments parallel to scan lines.

Quantification of instantaneous flow rate and dynamically changing effective orifice area using a geometry independent three-dimensional digital color Doppler method: An in vitro study mimicking mitral regurgitation.

OBJECTIVE: Our study was intended to test the accuracy of a 3-dimensional (3D) digital color Doppler flow convergence (FC) method for assessing the effective orifice area (EOA) in a new dynamic orifice model mimicking a variety of mitral regurgitation. BACKGROUND: FC surface area methods for detecting EOA have been reported to be useful for quantifying the severity of valvular regurgitation. With our new 3D digital direct FC method, all raw velocity data are available and variable Nyquist limits can be selected for computation of direct FC surface area for computing instantaneous flow rate and temporal change of EOA. METHODS: A 7.0-MHz multiplane transesophageal probe from an ultrasound system (ATL HDI 5000) was linked and controlled by a computer workstation to provide 3D images. Three differently shaped latex orifices (zigzag, arc, and straight slit, each with cutting-edge length of 1 cm) were used to mimic the dynamic orifice of mitral regurgitation. 3D FC surface computation was performed on parallel slices through the 3D data set at aliasing velocities (14-48 cm/s) selected to maximize the regularity and minimize lateral dropout of the visualized 3D FC at 5 points per cardiac cycle. Using continuous wave velocity for each, 3D-calculated EOA was compared with EOA determined by using continuous wave Doppler and the flow rate from a reference ultrasonic flow meter. Simultaneous digital video images were also recorded to define the actual orifice size for 9 stroke volumes (15-55 mL/beat with maximum flow rates 45-182 mL/s). RESULTS: Over the 9 pulsatile flow states and 3 orifices, 3D FC EOAs (0.05-0.63 cm(2)) from different phases of the cardiac cycle in each pump setting correlated well with reference EOA (r = 0.89-0.92, SEE = 0.027-0.055cm(2)) and they also correlated well with digital video images of the actual orifice peak (r = 0.97-0.98, SEE = 0.016-0.019 cm(2)), although they were consistently smaller, as expected by the contraction coefficient. CONCLUSION: The digital 3D FC method can accurately predict flow rate, and, thus, EOA (in conjunction with continuous wave Doppler), because it allows direct FC surface measurement despite temporal variability of FC shape.

A validation study of aortic stroke volume using dynamic 4-dimensional color Doppler: an in vivo study.

OBJECTIVE: To explore the feasibility of directly quantifying transaortic stroke volume with a newly developed dynamic 3-dimensional (3D) color Doppler flow measurement technique, an in vivo experimental study was performed. BACKGROUND: Traditional methods for flow quantification require geometric assumptions about flow area and flow profiles. Accurate quantification of flow across the aortic valve is clinically important as a means of estimating cardiac output. METHODS: Eight open-chest sheep were scanned with apical epicardial placement of a 7 to 4 MHz multiplane transesophageal probe scanning parallel to aortic flow and running on an ATL HDI 5000 system. An electromagnetic flow meter implanted on the ascending aorta was used as reference. Thirty different hemodynamic conditions were studied after steady states were obtained in the animals by administration of blood, angiotensin, and sodium nitroprusside. Electrocardiogram-gated digital color 3D velocity data were acquired for each of the 30 steady states. The aortic stroke volumes were computed by temporal and spatial integration of flow areas and actual velocities across a projected surface perpendicular to the direction of flow, at a level just below the aortic valve. RESULTS: There was close correlation between the 3D color Doppler calculated aortic stroke volumes and the electromagnetic data (r = 0.91, y = 0.96x + 1.01, standard error of the estimate = 2.6 mL/beat). CONCLUSION: Our results showed that dynamic 3D color Doppler measurements obtained in an open-chest animals provide the basis for accurate, geometry-independent quantitative evaluation of the aortic flow. Therefore, 3D digital color Doppler flow computation could potentially represent an important method for noninvasively determining cardiac output in patients.

A new dynamic three-dimensional digital color doppler method for quantification of pulmonary regurgitation: validation study in an animal model.

OBJECTIVES: The purpose of the present study was to validate a newly developed three-dimensional (3D) digital color Doppler method for quantifying pulmonary regurgitation (PR), using an animal model of chronic PR. BACKGROUND: Spectral Doppler methods cannot reliably be used to assess pulmonary regurgitation. METHODS: In eight sheep with surgically created PR, 27 different hemodynamic states were studied. Pulmonary and aortic electromagnetic (EM) probes and meters were used to provide reference right ventricular (RV) forward and pulmonary regurgitant stroke volumes. A multiplane transesophageal probe was placed directly on the RV and aimed at the RV outflow tract. Electrocardiogram-gated and rotational 3D scans were performed for acquiring dynamic 3D digital velocity data. After 3D digital Doppler data were transferred to a computer workstation, the RV forward and pulmonary regurgitant flow volumes were obtained by a program that computes the velocity vectors over a spherical surface perpendicular to the direction of scanning. RESULTS: Pulmonary regurgitant volumes and RV forward stroke volumes computed by the 3D method correlated well with those by the EM method (r = 0.95, mean difference = 0.51 +/- 1.89 ml/beat for the pulmonary regurgitant volume; and r = 0.91, mean difference = -0.22 +/- 3.44 ml/beat for the RV stroke volume). As a result of these measurements, the regurgitant fractions derived by the 3D method agreed well with the reference data (r = 0.94, mean difference = 2.06 +/- 6.11%). CONCLUSIONS: The 3D digital color Doppler technique is a promising method for determining pulmonary regurgitant volumes and regurgitant fractions. It should have an important application in clinical settings.

Direct quantification of transmitral flow volume with dynamic 3-dimensional digital color Doppler: a validation study in an animal model.

Accurately quantifying transmitral flow volume is clinically important not only as a measure of cardiac output, but also as a value from which to subtract aortic flow, for determining the severity of mitral regurgitation. However, controversy exists over the accuracy of pulsed Doppler for mitral flow quantification because of the complexity of mitral flow geometry and dynamic changes in flow profile and flow area. To explore the feasibility of directly quantifying transmitral flow volume with a newly developed dynamic 3-dimensional digital color Doppler technique, this in vivo experimental study was conducted to validate the method. Eight open chest sheep were imaged with a multiplane transesophageal (TEE) probe placed on the heart for digital 3-dimensional gated acquisition of mitral inflow over a 180-degree acquisition. The digital velocity data were contour detected for flow area after computing the velocity vectors and flow profile perpendicular to a spherical 3-dimensional surface across the mitral annulus. Flow areas and actual velocities were then integrated in time and space and the resulting flow volumes were compared with those obtained by a reference electromagnetic flowmeter on the aorta for 26 steady hemodynamic states. The flow volumes correlated closely to the electromagnetic references (y = 0.87x + 2.49, r = 0.92, SEE = 1.9 Ml per beat). Our study shows that transmitral flow volume can be accurately determined in vivo by this dynamic 3-dimensional digital color Doppler flow quantification method.

Assessment of pulmonary artery stenosis using freehand "flock of birds" digital color three-dimensional echocardiographic reconstruction.

Pulmonary artery (PA) trunk or branch PA stenosis is commonly found in patients with congenital heart disease. The aim of the present study was to evaluate the freehand "Flock of Birds" color Doppler three-dimensional (3D) reconstruction on a modeled-segment imitating PA stenosis. First, a PA model was created from latex tubes to simulate the main PA and its main branches with baseline cross-sectional areas (CSA) of 0.7 cm2. A series of narrowed segments in the right and left PA were created. The cross-sections of the smallest area ranged from 0.13 to 0.59 cm2 and stenotic segmental length ranged from 0.17 to 1.80 cm. The dimensions of these elements mounted on to the model were verified by intravascular ultrasound (IVUS) imaging. Next, pulsatile flows at 60 beats/ min were generated through the system. A GE/VingMed System FiVe with magnetic locator system (Flock of Birds) on a 3.5 MHz transducer was used to acquire a freehand sweep for ECG gated 3D data acquisition of color Doppler flows through the model. The images were reconstructed by EchoPac 3D software and the morphology of the stenotic elements were determined. The results revealed that the narrowest CSA determined by the 3D color flow cast of the pulmonary artery were in excellent agreement with IVUS CSA (r = 0.98, p < 0.001, SEE = 0.04 cm2). The stenotic length estimated from 3D was also in good agreement with the IVUS (r = 0.98, p < 0.001, SEE = 0.03 cm). In addition, complex morphology of the stenosis was well visualized by this technique. As a result, the noninvasive free-hand digital color 3D echocardiography can be adopted for the accurate assessment of the severity and morphology of PA stenosis in patients with congenital heart diseases.